差分方程就是针对要解决的目标，引入系统或过程中的离散变量，根据实际背景的规律、性质、平衡关系，建立离散变量所满足的平衡关系等式，从而建立差分方程。通过求出和分析方程的解，或者分析得到方程解的 特别性质（平衡性、稳定性、渐近性、振动性、周期性等），从而把握这个离散变量的变化过程的规律，进一步再结合其他分析，得到原问题的解(The difference equation is to establish the difference equation according to the law of the actual background, the nature and the balance relation, and establish the equilibrium relation equation which the discrete variable satisfies for the discrete target of the system or process. By solving and analyzing the solution of the equation, or by analyzing the special properties (balance, stability, asymptotic behavior, oscillation, periodicity, etc.) of the equation, we can grasp the law of the change process of this discrete variable, Other analysis, get the original solution)